This invention relates to butterfly valves.
Butterfly valves used in conventional piping systems typically employ a valve body which is internally and/or externally threaded at the opposite ends for connection to the piping system. When it is necessary to remove such a butterfly valve for replacement or repair, it usually is necessary to disassemble or loosen certain components of the piping system. Also, the valve usually cannot be rotated to a different position for more convenient location of the operating handle without disturbing the piping system.
Fabrication costs of certain valve components can be reduced by using conventional powder-metallurgy processes because finish machining is minimized. In powder-metallurgy processes, metal powders including small percentages of lubricant are compressed into the desired shape in a mold and are then sintered in a furnace with a non-oxidizing atmosphere to develop metallic properties. The sintering temperature usually is far enough below the melting point so there is no change in shape and size other than a small shrinkage or, in some cases, a slight expansion. The powders must be uniformly compressed throughout the resultant part in order to obtain the desired structural characteristics. The above-mentioned type of valve bodies for butterfly valves normally are too long to afford production by present commercial powder-metallurgy processes.